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U-DiTs: Downsample Tokens in U-Shaped Diffusion Transformers

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arxiv 2405.02730 v3 pith:G5EM5IWW submitted 2024-05-04 cs.CV

classification cs.CV
keywords u-netditsarchitecturediffusionu-ditcomputationconductdemonstrate
verification ladder T0 review T1 audit T2 compute T3 formal

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Diffusion Transformers (DiTs) introduce the transformer architecture to diffusion tasks for latent-space image generation. With an isotropic architecture that chains a series of transformer blocks, DiTs demonstrate competitive performance and good scalability; but meanwhile, the abandonment of U-Net by DiTs and their following improvements is worth rethinking. To this end, we conduct a simple toy experiment by comparing a U-Net architectured DiT with an isotropic one. It turns out that the U-Net architecture only gain a slight advantage amid the U-Net inductive bias, indicating potential redundancies within the U-Net-style DiT. Inspired by the discovery that U-Net backbone features are low-frequency-dominated, we perform token downsampling on the query-key-value tuple for self-attention that bring further improvements despite a considerable amount of reduction in computation. Based on self-attention with downsampled tokens, we propose a series of U-shaped DiTs (U-DiTs) in the paper and conduct extensive experiments to demonstrate the extraordinary performance of U-DiT models. The proposed U-DiT could outperform DiT-XL/2 with only 1/6 of its computation cost. Codes are available at https://github.com/YuchuanTian/U-DiT.

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Forward citations

Cited by 11 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. UniMC: Taming Diffusion Transformer for Unified Keypoint-Guided Multi-Class Image Generation

    cs.CV 2025-07 conditional novelty 7.0 of 10

    UniMC uses tokenized instance conditions (class, box, keypoints) and a timestep-aware modulator in a DiT backbone to control multi-class human and animal image generation, trained and evaluated on the new HAIG-2.9M dataset.

  2. TinyFusion: Diffusion Transformers Learned Shallow

    cs.CV 2024-12 conditional novelty 7.0 of 10

    A learnable depth-pruning method that optimizes post-fine-tuning recoverability produces a 14-layer DiT-XL with FID 2.86 and a 2x speedup at 7% of the original training cost.

  3. Unveiling the Secret of AdaLN-Zero in Diffusion Transformer

    cs.CV 2026-08 conditional novelty 6.0 of 10

    Zero-initializing the modulation weights is the dominant reason adaLN-Zero outperforms adaLN, and replacing it with a Gaussian initialization of std 0.001 improves FID at the same training steps.

  4. Amortized Moment Matching for Visual Generation

    cs.LG 2026-07 accept novelty 6.0 of 10

    Amortized Fréchet Distance uses neural nets to match conditional means and covariances, yielding stronger one-step visual generators than explicit FD-loss or multi-step teachers.

  5. DiffSparse: Accelerating Diffusion Transformers with Learned Token Sparsity

    cs.CV 2026-04 conditional novelty 6.0 of 10

    A learnable cost predictor plus dynamic programming allocates layer-wise token sparsity for diffusion transformers, removing forced full steps and cutting ~54% compute on PixArt-α without quality loss.

  6. PiT: Progressive Diffusion Transformer

    cs.CV 2025-05 conditional novelty 6.0 of 10

    PiT replaces global attention in diffusion transformers with window attention plus a depthwise-conv bridging branch and a progressive channel schedule, achieving better FID than DiT and U-DiT at lower or similar compute.

  7. Ingredients: Blending Custom Photos with Video Diffusion Transformers

    cs.CV 2025-01 conditional novelty 6.0 of 10

    Ingredients adds a mask-supervised identity router to a video diffusion transformer, enabling multi-person videos from a few reference photos without per-identity fine-tuning.

  8. Identity-Preserving Text-to-Video Generation by Frequency Decomposition

    cs.CV 2024-11 conditional novelty 6.0 of 10

    ConsisID generates identity-preserving videos by injecting low-frequency facial features into shallow layers and high-frequency identity features into attention blocks of a DiT video model.

  9. Align Your Flow: Scaling Continuous-Time Flow Map Distillation

    cs.CV 2025-06 conditional novelty 5.0 of 10

    Align Your Flow distills flow maps with new continuous-time objectives and autoguidance, achieving state-of-the-art few-step FID on ImageNet and strong text-to-image results.

  10. RainFusion: Adaptive Video Generation Acceleration via Multi-Dimensional Visual Redundancy

    cs.CV 2025-05 conditional novelty 5.0 of 10

    Training-free sparse attention that classifies each head as spatial, temporal, or textural and applies a matched mask or token reduction, giving about 1.9x attention speedup with small VBench losses.

  11. LaVin-DiT: Large Vision Diffusion Transformer

    cs.CV 2024-11 conditional novelty 5.0 of 10

    A single diffusion transformer with a spatial-temporal VAE and in-context example pairs unifies over 20 vision tasks, with strong scores on several image benchmarks and uneven evidence on video tasks.

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